Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)
by Randy Taylor, Advanced Tooling Corporation
What's the Maximum Thickness of Hard Chrome Plating?
Q. What could the the maximum thickness of hard chrome plating that can be deposited on ferrous metal after which the layer starts disintegrating?
Is there any measure of adhesion which can be checked, if so, the method to check?
A. If properly applied, there is no set limit to the thickness of hard chrome, but as a general rule, chromium is most stable on ferrous alloys in the range of 0.0005 to about 0.025 in a single application. Chromium deposits over 0.025 per side can begin to become rough with build up at edges and pitting. Success with thick chromium deposits has a lot to do with the initial surface finish of the base metal.
When applicable, "after plate finish requirements", i.e., uniformity, mimimum thickness, surface micro finish and micro-crack acceptance level, dictate the best chromium procedure to follow. The initial set up, tooling and especially anoding procedures, are critical steps to achieving the most success.
Chromium deposits can be applied in numerous ways, with a variety of results to achieve specific customer requirements. One such procedure is to apply a layer of chromium over top a layer of nickel, when coating thickness requirements exceed 0.025 (per side).